Analytic rrect clip for cicular corners, radius >= 0.5
BUG=skia:2181
R=robertphillips@google.com, jvanverth@google.com
Author: bsalomon@google.com
Review URL: https://codereview.chromium.org/171413004
git-svn-id: http://skia.googlecode.com/svn/trunk@13498 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/effects/GrRRectEffect.cpp b/src/gpu/effects/GrRRectEffect.cpp
new file mode 100644
index 0000000..a2a6af7
--- /dev/null
+++ b/src/gpu/effects/GrRRectEffect.cpp
@@ -0,0 +1,155 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrRRectEffect.h"
+
+#include "gl/GrGLEffect.h"
+#include "gl/GrGLSL.h"
+#include "GrTBackendEffectFactory.h"
+
+#include "SkPath.h"
+
+// This effect only supports circular corner rrects where all corners have the same radius
+// which must be <= kRadiusMin.
+static const SkScalar kRadiusMin = 0.5;
+
+//////////////////////////////////////////////////////////////////////////////
+class GrGLRRectEffect : public GrGLEffect {
+public:
+ GrGLRRectEffect(const GrBackendEffectFactory&, const GrDrawEffect&);
+
+ virtual void emitCode(GrGLShaderBuilder* builder,
+ const GrDrawEffect& drawEffect,
+ EffectKey key,
+ const char* outputColor,
+ const char* inputColor,
+ const TransformedCoordsArray&,
+ const TextureSamplerArray&) SK_OVERRIDE;
+
+ static inline EffectKey GenKey(const GrDrawEffect&, const GrGLCaps&) { return 0; }
+
+ virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;
+
+private:
+ GrGLUniformManager::UniformHandle fInnerRectUniform;
+ GrGLUniformManager::UniformHandle fRadiusPlusHalfUniform;
+ SkRRect fPrevRRect;
+ typedef GrGLEffect INHERITED;
+};
+
+GrGLRRectEffect::GrGLRRectEffect(const GrBackendEffectFactory& factory,
+ const GrDrawEffect& drawEffect)
+ : INHERITED (factory) {
+ fPrevRRect.setEmpty();
+}
+
+void GrGLRRectEffect::emitCode(GrGLShaderBuilder* builder,
+ const GrDrawEffect& drawEffect,
+ EffectKey key,
+ const char* outputColor,
+ const char* inputColor,
+ const TransformedCoordsArray&,
+ const TextureSamplerArray& samplers) {
+ const char *rectName;
+ const char *radiusPlusHalfName;
+ // The inner rect is the rrect bounds inset by the radius. Its top, left, right, and bottom
+ // edges correspond to components x, y, z, and w, respectively.
+ fInnerRectUniform = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
+ kVec4f_GrSLType,
+ "innerRect",
+ &rectName);
+ fRadiusPlusHalfUniform = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
+ kFloat_GrSLType,
+ "radiusPlusHalf",
+ &radiusPlusHalfName);
+ const char* fragmentPos = builder->fragmentPosition();
+ // At each quarter-circle corner we compute a vector that is the offset of the fragment position
+ // from the circle center. The vector is pinned in x and y to be in the quarter-plane relevant
+ // to that corner. This means that points near the interior near the rrect top edge will have
+ // a vector that points straight up for both the TL left and TR corners. Computing an
+ // alpha from this vector at either the TR or TL corner will give the correct result. Similarly,
+ // fragments near the other three edges will get the correct AA. Fragments in the interior of
+ // the rrect will have a (0,0) vector at all four corners. So long as the radius > 0.5 they will
+ // correctly produce an alpha value of 1 at all four corners. We take the min of all the alphas.
+ // The code below is a simplified version of the above that performs maxs on the vector
+ // components before computing distances and alpha values so that only one distance computation
+ // need be computed to determine the min alpha.
+ builder->fsCodeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
+ builder->fsCodeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
+ builder->fsCodeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
+ builder->fsCodeAppendf("\t\tfloat alpha = clamp(%s - length(dxy), 0.0, 1.0);\n",
+ radiusPlusHalfName);
+
+ builder->fsCodeAppendf("\t\t%s = %s;\n", outputColor,
+ (GrGLSLExpr4(inputColor) * GrGLSLExpr1("alpha")).c_str());
+}
+
+void GrGLRRectEffect::setData(const GrGLUniformManager& uman, const GrDrawEffect& drawEffect) {
+ const GrRRectEffect& rre = drawEffect.castEffect<GrRRectEffect>();
+ const SkRRect& rrect = rre.getRRect();
+ if (rrect != fPrevRRect) {
+ SkASSERT(rrect.isSimpleCircular());
+ SkRect rect = rrect.getBounds();
+ SkScalar radius = rrect.getSimpleRadii().fX;
+ SkASSERT(radius >= kRadiusMin);
+ rect.inset(radius, radius);
+ uman.set4f(fInnerRectUniform, rect.fLeft, rect.fTop, rect.fRight, rect.fBottom);
+ uman.set1f(fRadiusPlusHalfUniform, radius + 0.5f);
+ fPrevRRect = rrect;
+ }
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+GrEffectRef* GrRRectEffect::Create(const SkRRect& rrect) {
+ if (!rrect.isSimpleCircular()) {
+ return NULL;
+ }
+ if (rrect.getSimpleRadii().fX < kRadiusMin) {
+ return NULL;
+ }
+ return CreateEffectRef(AutoEffectUnref(SkNEW_ARGS(GrRRectEffect, (rrect))));
+}
+
+GrRRectEffect::~GrRRectEffect() {}
+
+void GrRRectEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
+ *validFlags = 0;
+}
+
+const GrBackendEffectFactory& GrRRectEffect::getFactory() const {
+ return GrTBackendEffectFactory<GrRRectEffect>::getInstance();
+}
+
+GrRRectEffect::GrRRectEffect(const SkRRect& rrect)
+ : fRRect(rrect) {
+ SkASSERT(rrect.isSimpleCircular());
+ SkASSERT(rrect.getSimpleRadii().fX >= kRadiusMin);
+ this->setWillReadFragmentPosition();
+}
+
+bool GrRRectEffect::onIsEqual(const GrEffect& other) const {
+ const GrRRectEffect& rre = CastEffect<GrRRectEffect>(other);
+ return fRRect == rre.fRRect;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+GR_DEFINE_EFFECT_TEST(GrRRectEffect);
+
+GrEffectRef* GrRRectEffect::TestCreate(SkRandom* random,
+ GrContext*,
+ const GrDrawTargetCaps& caps,
+ GrTexture*[]) {
+ SkScalar w = random->nextRangeScalar(20.f, 1000.f);
+ SkScalar h = random->nextRangeScalar(20.f, 1000.f);
+ SkScalar r = random->nextRangeF(kRadiusMin, 9.f);
+ SkRRect rrect;
+ rrect.setRectXY(SkRect::MakeWH(w, h), r, r);
+
+ return GrRRectEffect::Create(rrect);
+}